1. Field
The disclosure relates generally to a photodetector and method and, more particularly, to a photodetector having ultra low dark current and a method for fabricating a photodetector having ultra low dark current.
2. Background
Dark current is a current that flows in a photodetector when it is not receiving any light, and is a significant source of noise in PIN photodetectors having high sensitivity. Current efforts to reduce dark current in PIN photodetectors focus primarily on reducing diffusion currents in the photodetector (the process of carriers distributing themselves from regions of high concentration to regions of low concentration) which is a significant contributor to dark current.
One known approach to reducing diffusion current is to uniformly dope the “intrinsic absorption” layer of the photodetector (see, for example, U.S. Pat. No. 6,573,581). Although this approach does reduce diffusion current, it fails to address generation current due to defects in the photodetector material or at a surface, which is also a major contributor to and actually dominates the total dark current in small pixels used for imaging arrays at or below room temperature.
There is, accordingly, a need for a photodetector that has very low dark current and to a method for fabricating a photodetector having a very low dark current.